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42. Optical Properties of Synthetic Diamond Single Crystals.

Author

Mudry&icaron;, A. V., Larionova, T. P., Shakin, I. A., Gusakov, G. A., Dubrov, G. A., and Tikhonov, V. V.

Subjects
DIAMOND crystals, CATALYSTS, LUMINESCENCE, PHOTOLUMINESCENCE, CRYSTALS, ABSORPTION
Abstract

Synthetic diamond single crystals were grown by the thermal gradient method in a high-pressure apparatus in the presence of solvent catalysts (nickel, iron). Absorption, luminescence, and photoluminescence excitation measurements were performed in order to determine the nature of impurity–defect complexes in both as-grown crystals and crystals treated at high temperature (T ≈ 2000–2200 K) and high pressure (P ≈ 6.0–6.5 GPa). Different luminescence and absorption bands were assigned to impurity centers containing nitrogen and nickel atoms. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Published
2004
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43. Structure and Properties of La0.6Sr0.4 – xBa xMnO3 (0 ≤ x ≤ 0.4) Magnetoresistive Ceramics.

Author

Pashchenko, V., Ul'yanov, A., Shemyakov, A., Khartsev, S., Mezin, N., Medvedev, Yu., Gusakov, G., and Turchenko, V.

Abstract

The effect of Ba content on the phase composition, lattice parameter, 55Mn NMR spectrum, resistance, and magnetoresistance of La0.6Sr0.4 – xBa xMnO3 perovskites was studied. The lattice parameter of the single-phase ceramic samples was found to increase with increasing x. The tolerance factor increases and the ionic field strength decreases as x increases from 0 to 0.4. The 55Mn NMR results obtained at 77 K indicate a high-frequency electron exchange between Mn3+ and Mn4+ in the ferromagnetic phase. The peak-magnetoresistance temperature tends to decrease with increasing x. The magnetoresistance of the ceramics is correlated with the bond covalence. It is inferred that the ceramics contain inhomogeneities differing in nature and length scale (macroscopic, mesoscopic, and microscopic), which influence their magnetoresistance. [ABSTRACT FROM AUTHOR]

Published
2002
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